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ISSN: 2056-9890
Volume 72| Part 2| February 2016| Pages 178-183

Two new polytypes of 2,4,6-tri­bromo­benzo­nitrile

aDepartment of Chemistry, University of Minnesota, Minneapolis, MN 55455-0431, USA
*Correspondence e-mail: nolan001@umn.edu

Edited by A. J. Lough, University of Toronto, Canada (Received 21 October 2015; accepted 5 January 2016; online 13 January 2016)

Three polymorphs of 2,4,6-tri­bromo­benzo­nitrile (RCN), C7H2Br3N, two of which are novel and one of which is a redetermination of the original structure first determined by Carter & Britton [(1972). Acta Cryst. B28, 945–950] are found to be polytypic. Each has a layer structure which differs only in the stacking of the layers. Each layer is composed of mol­ecules associated through C≡N⋯Br contacts which form R22(10) rings. Two such rings are associated with each N atom; one with each ortho-Br atom. No new polytypes of 1,3,5-tri­bromo-2-iso­cyano­benzene (RNC) were found but a re-determination of the original structure by Carter et al. [(1977). Cryst. Struct. Commun. 6, 543–548] is presented. RNC was found to be isostructural with one of the novel polytypes of RCN. Unit cells were determined for 23 RCN samples and 11 RNC samples. Polytypes could not be distinguished based on crystal habits. In all four structures, each mol­ecule of the asymmetric unit lies across a mirror plane.

1. Chemical context

The reported structures of 2,4,6-tri­bromo­benzo­nitrile (RCN, Figs. 1[link] and 2[link]; Carter & Britton, 1972[Carter, V. B. & Britton, D. (1972). Acta Cryst. B28, 945-950.]) and 1,3,5-tri­bromo-2-iso­cyano­benzene (RNC, Figs. 1[link] and 3[link]; Carter et al., 1977[Carter, V. B., Britton, D. & Gleason, W. G. (1977). Cryst. Struct. Commun. 6, 543-548.]) have two-dimensional layers of similarly arranged mol­ecules, but the packing of adjacent layers is distinctly different. At the time, no explanation was offered. It was puzzling, given that the two compounds are isoelectronic, isosteric, and the principal inter­molecular inter­actions, C≡N⋯Br and N≡C⋯Br, are similar. Recent reports of polytype organic structures, such as picryl bromide (Parrish et al., 2008[Parrish, D. A., Deschamps, J. R., Gilardi, R. D. & Butcher, R. J. (2008). Cryst. Growth Des. 8, 57-62.]) and 5,6-di­methyl­benzofurazan 1-oxide (Britton et al., 2012[Britton, D., Young, V. G., Noland, W. E., Pinnow, M. J. & Clark, C. M. (2012). Acta Cryst. B68, 536-542.]) led to the idea that RCN and RNC might occur as polytypes. Earlier, Bredig (1930[Bredig, M. A. (1930). Z. Kristallogr. 74, 56-61.]) had determined the space group and unit cell of RCN with the same results as Carter & Britton. Bredig was trying to follow up on the goniometer studies of Jaeger (1909[Jaeger, F. M. (1909). Z. Kristallogr. 46, 268-269.]), but while he found the same a:b ratio as Jaeger in the RCN unit cell, he found a different b:c ratio.

[Scheme 1]
[Figure 1]
Figure 1
Synthesis of RCN and RNC.
[Figure 2]
Figure 2
Mol­ecular structures, with atom labeling, of RCN-I viewed along [11[\overline{1}]]; RCN-II viewed along [120]; RCN-III viewed along [120]. Displacement ellipsoids are drawn at the 50% probability level. In discussion, mol­ecules are named by their respective nitro­gen atoms. Each mol­ecule lies across a crystallographic mirror plane.
[Figure 3]
Figure 3
Mol­ecular structure, with atom labeling, of RNC-II viewed along [120]. Displacement ellipsoids are drawn at the 50% probability level. Each mol­ecule lies across a crystallographic mirror plane.

Accordingly, a search was made for polytypes of RCN, and to a lesser extent, of RNC. Four different structures were identified. RCN-I is the original Z = 2 structure of RCN; RCN-II is a new Z = 8 polytype; RCN-III is a new Z = 12 polytype. No RNC counterparts to RCN-I or RCN-III were observed. RNC-II is the original Z = 8 structure. As the Z values suggest, RCN-II and RNC-II are isomorphs.

2. Structural commentary

Mol­ecules of RCN and RNC are nearly planar. The average distance of atoms from the plane of best fit is 0.025 Å in RCN-I. For RCN-II, the average distances are 0.037 and 0.010 Å, for the (N27) and (N37) mol­ecules, respectively. In RNC-II, the mol­ecules are slightly more distorted, with average deviations of 0.043 and 0.017 Å for the (N127) and (N137) mol­ecules, respectively. For RCN-III, the average distances are 0.009, 0.018, and 0.032 Å for the (N47), (N57), and (N67) mol­ecules, respectively.

The bond lengths in RCN and RNC are generally similar (Fig. 4[link]). They are also similar to the mean bond distances reported for bonds of each type (Allen et al., 1987[Allen, F. H., Kennard, O., Watson, D. G., Brammer, L., Orpen, A. G. & Taylor, R. (1987). J. Chem. Soc. Perkin Trans. 2, S1-19.]). The N atom in RNC is displaced toward the aryl ring compared to the literature distances for aryl isocyanides.

[Figure 4]
Figure 4
Selected bond lengths (Å) in RCN and RNC, averaged across all polytypes. The data shown in parentheses are the mean distances for each bond type reported by Allen et al. (1987[Allen, F. H., Kennard, O., Watson, D. G., Brammer, L., Orpen, A. G. & Taylor, R. (1987). J. Chem. Soc. Perkin Trans. 2, S1-19.]).

3. Supra­molecular features

Fig. 5[link] shows a two-dimensional layer of RCN-I. All of the structures are composed of similar layers. Adjacent mol­ecules are associated through C≡N⋯Br inter­actions, arranged in R22(10) rings (Etter, 1990[Etter, M. C. (1990). Acc. Chem. Res. 23, 120-126.]; Bernstein et al., 1995[Bernstein, J., Davis, R. E., Shimoni, L. & Chang, N.-L. (1995). Angew. Chem. Int. Ed. Engl. 34, 1555-1573.]). The CN⋯Br distances in these rings range between 3.053 and 3.077 Å (Table 1[link]); these distances can be compared with the N⋯Br van der Waals distance of 3.40 Å (Bondi, 1964[Bondi, A. (1964). J. Phys. Chem. 68, 441-451.]; Rowland & Taylor, 1996[Rowland, R. S. & Taylor, R. (1996). J. Phys. Chem. 100, 7384-7391.]). Each layer in RCN-II is composed of alternating (N27) and (N37) mol­ecules. RCN-III contains two layers of alternating (N47) and (N57) mol­ecules for each layer composed entirely of (N67) mol­ecules. Adjacent pairs of layers show translational or pseudotranslational, or pseudocentric stacking (Fig. 6[link]). RCN-I shows translational stacking between all adjacent layers (Fig. 7[link]). In RCN-II, alternating pairs of layers show pseudocentric and pseudotranslational stacking (Fig. 8[link]). In RCN-III, each layer of (N67) mol­ecules pseudotranslationally overlaps both neighboring (N47/N57) layers, while pairs of adjacent (N47/N57) layers, every third pair of layers, overlap pseudocentrically (Fig. 9[link]).

Table 1
Short contact geometry (Å, °)

XY⋯Br XY Y⋯Br XY⋯Br
C17≡N17⋯Br12i 1.144 (10) 3.053 (4) 131.45 (9)
C27≡N27⋯Br32ii 1.132 (7) 3.059 (3) 131.76 (7)
N127≡C127⋯Br132ii 1.147 (6) 3.141 (4) 134.01 (8)
C37≡N37⋯Br22iii 1.156 (6) 3.077 (3) 130.68 (10)
N137≡C137⋯Br122iii 1.164 (6) 3.161 (4) 133.23 (11)
C47≡N47⋯Br52ii 1.146 (6) 3.072 (3) 130.95 (9)
C57≡N57⋯Br42iii 1.147 (6) 3.057 (3) 131.47 (7)
C67≡N67⋯Br62iv 1.139 (6) 3.065 (3) 131.96 (7)
Symmetry codes: (i) −x, 1 − y, −z; (ii) x, y, −1 + z; (iii) x, y, 1 + z; (iv) 1 − x, 1 − y, 1 − z.
[Figure 5]
Figure 5
View of one layer of RCN-I along [10[\overline{1}]]. Dashed blue lines represent short contacts.
[Figure 6]
Figure 6
Pseudotranslational (T) and pseudocentric (C) stacking of layers in RCN-II and RCN-III, respectively. Both are viewed along [100]. The mol­ecules shown are the second pair of layers from the top, in Fig. 7[link] and Fig. 8[link], respectively.
[Figure 7]
Figure 7
Translational (T) stacking of layers in Z = 2 RCN-I, viewed along [110]. If the unit cell of RCN-I is transformed by the matrix [100/010/201], the dimensions of the projection become 10.247 (3) × 12.480 (3) Å, which is similar to the corresponding b × c measurements, 10.2147 (10) × 12.4754 (12) Å for RCN-II, and 10.2167 (18) × 12.493 (2) Å for RCN-III.
[Figure 8]
Figure 8
Pseudocentric (C) and pseudotranslational (T) stacking of layers in Z = 8 RCN-II, viewed roughly along [010].
[Figure 9]
Figure 9
Pseudotranslational (T) and pseudocentric (C) stacking of layers in Z = 12 RCN-III, viewed roughly along [010].

The NC⋯Br contact distances in RNC-II are a smaller percentage of the van der Waals distance, 3.63 Å, versus corresponding atoms in RCN-II. The contacts in RNC-II occur at slightly wider angles than those in RCN-II (Table 1[link]).

In RCN-II, the planes of best fit of the two different mol­ecules are inclined by 6.5° to each other; in RNC-II this inclination is 7.5°. In RCN-III, the relative inclination of planes of (N47) and (N57) mol­ecules is 7.0°. These two planes are approximately bis­ected by the planes of (N67) mol­ecules.

4. Database survey

A search of the Cambridge Structural Database (Version 5.36, update 3; Groom & Allen, 2014[Groom, C. R. & Allen, F. H. (2014). Angew. Chem. Int. Ed. 53, 662-671.]) for 2,4,6-trihalo-3,5-unsubstituted benzo­nitriles found nine entries: RCN; its tri­chloro analog, Gol'der et al. (1952[Gol'der, G. A., Zhdanov, G. S. & Umanskij, M. M. (1952). Russ. J. Phys. Chem. 26, 1434-1437.]), Carter & Britton (1972[Carter, V. B. & Britton, D. (1972). Acta Cryst. B28, 945-950.]), Pink et al. (2000[Pink, M., Britton, D., Noland, W. E. & Pinnow, M. J. (2000). Acta Cryst. C56, 1271-1273.]); its tri­fluoro analog, Britton (2008[Britton, D. (2008). Acta Cryst. C64, o583-o585.]); four mixed-halogen entries, Gleason & Britton (1978[Gleason, W. B. & Britton, D. (1978). Cryst. Struct. Commun. 7, 365-370.]), Britton (2005[Britton, D. (2005). Acta Cryst. E61, o1726-o1727.]), Britton et al. (2002[Britton, D., Noland, W. E. & Henke, T. K. (2002). Acta Cryst. E58, o185-o187.]), and Britton (1997[Britton, D. (1997). Acta Cryst. C53, 225-227.]). Searching for the corresponding isocyanides found two entries: RNC and its tri­chloro analog (Pink et al., 2000[Pink, M., Britton, D., Noland, W. E. & Pinnow, M. J. (2000). Acta Cryst. C56, 1271-1273.]).

Layers of the type observed in RCN were reported in 2,6-di­bromo entries with Cl, Br, or I at the 4-position. Other entries exhibit short contacts between the cyano- or iso­cyano- group and one ortho-halogen atom of an intra­layer mol­ecule, with various inter­layer contacts. Polymorphs are only reported for 2,4,6-tri­chloro­benzo­nitrile; those are not polytypic.

Expanding the search to include organometallic complexes found three more entries, with the cyano N or iso­cyano C atom ligating gallium (tri­fluoro­benzo­nitrile; Tang et al., 2012[Tang, S., Monot, J., El-Hellani, A., Michelet, B., Guillot, R., Bour, C. & Gandon, V. (2012). Chem. Eur. J. 18, 10239-10243.]), rhenium (tri­chloro­iso­cyano­benzene; Ko et al., 2011[Ko, C.-C., Siu, J. W.-K., Cheung, A. W.-Y. & Yiu, S.-M. (2011). Organometallics, 30, 2701-2711.]), and ruthenium (RNC; Leung et al., 2009[Leung, C.-F., Ng, S.-M., Xiang, J., Wong, W.-Y., Lam, M. H.-W., Ko, C.-C. & Lau, T.-C. (2009). Organometallics, 28, 5709-5714.]).

5. Synthesis and crystallization

2,4,6-Tri­bromo­aniline was prepared from aniline according to the work of Coleman & Talbot (1943[Coleman, G. H. & Talbot, W. F. (1943). Org. Synth, Coll. Vol. 2, 592-595.]).

RCN, adapted from the work of Toya et al. (1992[Toya, Y., Takagi, M., Nakata, H., Suzuki, N., Isobe, M. & Goto, T. (1992). Bull. Chem. Soc. Jpn, 65, 392-395.]): Diazo­tization: 2,4,6-Tri­bromo­aniline (1.25 g), water (2.5 ml), and glacial acetic acid (4.4 ml) were combined in a round-bottomed flask. The resulting suspension was cooled in an ice bath, and then H2SO4 (98%, 1.0 ml) was added dropwise, followed by an ice-cold solution of NaNO2 (520 mg) in water (4 ml). The resulting mixture was warmed to 310 K for 1 h, and then cooled in an ice bath. Cyanide suspension: CuCN (680 mg) and NaCN (1.12 g) were dissolved in water (20 ml). NaHCO3 (10.9 g) and ethyl acetate (10 ml) were added, giving a suspension, which was cooled in an ice bath. Cyanation: The diazo­tization mixture was added dropwise to the cyanide suspension as quickly as possible without causing excessive foaming. The ice bath was removed and then the mixture was stirred overnight. The organic phase was set aside. The aqueous phase was extracted with ethyl acetate (3 × 10 ml). The combined organic portions were washed with brine (10 ml), dried with Na2SO4, and concentrated at reduced pressure, giving a brown powder, which was purified by column chromatography (SiO2, hexa­ne–ethyl acetate, gradient from 1:0 to 10:1). The desired fraction (Rf = 0.61 in 8:1) was concentrated at reduced pressure, giving beige needles (760 mg, 59%). M.p. 400–400.5 K (lit. 402 K; Giumanini et al., 1996[Giumanini, A. G., Verardo, G., Geatti, P. & Strazzolini, P. (1996). Tetrahedron, 52, 7137-7148.]); 1H NMR (300 MHz, CD2Cl2) δ 7.853 (s, H13); 13C NMR (75 MHz, CD2Cl2) δ 135.3 (C13), 128.6 (C14), 127.4 (C12), 118.3 (C17), 116.0 (C11); IR (NaCl, cm−1) 3095, 3068, 2921 (w), 2233 (s, C≡N; lit. 2232), 1716 (w), 1563 (s), 1527 (s), 1431 (s), 1410 (s), 1370 (s), 1353 (s), 1328, 1191 (s), 1109 (s), 1087, 1063 (s), 854 (s), 809 (s), 748 (s); MS (EI, m/z) [M]+ calculated for C7H2Br3N 336.7732, found 336.7716.

2,4,6-Tri­bromo­formanilide, adapted from the work of Krishnamurthy (1982[Krishnamurthy, S. (1982). Tetrahedron Lett. 23, 3315-3318.]): Acetic anhydride (3.2 ml) and tetra­hydro­furan (THF, 5.0 ml) were combined in a round-bottomed flask. Formic acid (88% aq., 1.7 ml) was added dropwise. The resulting solution was stirred for 30 min at room temperature. A solution of 2,4,6-tri­bromo­aniline (1.82 g) in THF (20 ml) was added dropwise. The resulting mixture was stirred for 18 h. The resulting heterogeneous mixture was filtered through neutral alumina (Sigma–Aldrich 199974, 5 cm H × 3 cm D), with addition of sufficient THF to elute all product, as indicated by TLC. The filtrate was concentrated at reduced pressure. The resulting residue was washed with sat. NaHCO3 solution (50 ml), and then filtered. The filter cake was recrystallized from acetone, giving white needles (1.72 g, 87%). M.p. 493–494 K (lit. 494.5 K; Chattaway et al., 1899[Chattaway, F. D., Orton, K. J. P. & Hurtley, W. H. (1899). Ber. Dtsch. Chem. Ges. 32, 3635-3638.]); Rf = 0.48 (SiO2 in 1:1 hexa­ne–ethyl acetate); 1H NMR (300 MHz, (CD3)2SO) δ 10.192 (s, NH, O-E conformer, 0.87H), 8.522 (s, NH, O-Z conformer, 0.13H), 8.260 (s, CHO, 1H), 8.018 (s, CH, 2H); 13C NMR (75 MHz, (CD3)2SO) δ 165.9 (CO, O-Z conformer), 159.8 (CO, O-E conformer), 134.6 (ipso-C), 134.4 (CH), 124.5 (ortho-CBr), 121.1 (para-CBr); IR (NaCl, cm−1) 3201, 3166, 1661 (s, C=O), 1558, 1154, 858, 810; MS (ESI, m/z) [M – H] calculated for C7H4Br3NO 355.7750, found 355.7758. Analysis (MHW Laboratories, Phoenix, AZ, USA) calculated for C7H4Br3NO: C 23.50, H 1.13, Br 66.99, N 3.91; found C 23.42, H 1.15, Br 66.71, N 3.57.

RNC, adapted from the work of Ugi et al. (1965[Ugi, I., Fetzer, U., Eholzer, U., Knupfer, H. & Offermann, K. (1965). Angew. Chem. Int. Ed. Engl. 4, 472-484.]): 2,4,6-Tri­bromo­formanilide (1.96 g) and N,N-diiso­propyl­ethyl­amine (DIPEA, 3.4 ml) were added to 1,2-di­chloro­ethane (75 ml). The resulting suspension was refluxed for 5 min, and then cooled to room temperature. POCl3 (0.6 ml) was added dropwise. The mixture was stirred for 18 h, cooled in an ice bath, and then filtered through neutral alumina (3 cm H × 3 cm D), with addition of sufficient di­chloro­methane (DCM) to elute all product as indicated by TLC. The filtrate was concentrated at reduced pressure. The resulting yellow residue was dissolved in DCM (25 ml), cooled in an ice bath, and washed with ice-cold acetic acid solution (0.025 M, 3 × 15 ml), and then ice-cold sat. NaHCO3 solution (15 ml). The organic phase was collected, dried with Na2SO4, and then concentrated under a stream of nitro­gen, giving beige needles upon filtration (630 mg, 34%). M.p. 390 K (lit. 394 K, Mironov & Mokrushin, 1999[Mironov, M. A. & Mokrushin, V. S. (1999). Russ. J. Org. Chem. 35, 693-697.]); Rf = 0.75 (Al2O3 in 2:1 hexa­ne–ethyl acetate); 1H NMR (300 MHz, CD2Cl2) δ 7.827 (s, H123); 13C NMR (75 MHz, (CD3)2CO) 159.7 (C127), 135.8 (C123), 135.4 (C121), 124.5 (C124), 122.0 (C122); IR (NaCl, cm−1) 3162, 3068, 2921, 2128 (s, N≡C; lit. 2125), 1660 (s), 1555 (s), 1370 (s), 856 (s), 701 (s); MS (EI, m/z) [M]+ calculated for C7H2Br3N 336.7732, found 336.7734.

Crystallization: RCN crystals were grown by slow evaporation of single-solvent solutions (290–295 K). RCN-I was obtained from aceto­nitrile, benzene, chloro­form, or methyl­ene chloride; RCN-II from mesitylene; RCN-III from benzene or chloro­form. RNC-II crystals were obtained by sublimation (385 K, 0.05 torr), or by slow evaporation from the same solvents as RCN (268–295 K).

6. Refinement

Crystal data, data collection, and structure refinement details for RCN and RNC are summarized in Table 2[link]. H atoms were placed in calculated positions and refined as riding atoms, with C—H = 0.95 Å and Uiso(H) = 1.2Ueq(C).

Table 2
Experimental details

  RCN-I RCN-II RCN-III RNC-II
Crystal data
Chemical formula C7H2Br3N C7H2Br3N C7H2Br3N C7H2Br3N
Mr 339.83 339.83 339.83 339.83
Crystal system, space group Monoclinic, P21/m Orthorhombic, Pnma Orthorhombic, Pnma Orthorhombic, Pnma
Temperature (K) 173 173 173 173
a, b, c (Å) 4.8742 (15), 10.247 (3), 8.683 (3) 13.6183 (13), 10.2147 (10), 12.4754 (12) 20.399 (4), 10.2167 (18), 12.493 (2) 13.5916 (18), 10.1464 (13), 12.6158 (16)
α, β, γ (°) 90, 94.97 (1), 90 90, 90, 90 90, 90, 90 90, 90, 90
V3) 432.0 (2) 1735.4 (3) 2603.7 (8) 1739.8 (4)
Z 2 8 12 8
Radiation type Mo Kα Mo Kα Mo Kα Mo Kα
μ (mm−1) 13.93 13.88 13.87 13.84
Crystal size (mm) 0.50 × 0.15 × 0.10 0.25 × 0.20 × 0.07 0.50 × 0.15 × 0.10 0.40 × 0.35 × 0.20
 
Data collection
Diffractometer Bruker 1K area detector Bruker 1K area detector Bruker 1K area detector Bruker APEXII CCD
Absorption correction Multi-scan (SADABS; Bruker, 2002[Bruker (2002). APEX2, SMART, SAINT, and SADABS. Bruker AXS, Inc., Madison, Wisconsin, USA.]) Multi-scan (SADABS; Bruker, 2002[Bruker (2002). APEX2, SMART, SAINT, and SADABS. Bruker AXS, Inc., Madison, Wisconsin, USA.]) Multi-scan (SADABS; Bruker, 2002[Bruker (2002). APEX2, SMART, SAINT, and SADABS. Bruker AXS, Inc., Madison, Wisconsin, USA.]) Multi-scan (SADABS; Bruker, 2002[Bruker (2002). APEX2, SMART, SAINT, and SADABS. Bruker AXS, Inc., Madison, Wisconsin, USA.])
Tmin, Tmax 0.080, 0.248 0.06, 0.37 0.054, 0.337 0.170, 0.333
No. of measured, independent and observed [I > 2σ(I)] reflections 4093, 1024, 856 16607, 2093, 1692 22804, 2691, 2165 19459, 2105, 1638
Rint 0.127 0.052 0.055 0.078
(sin θ/λ)max−1) 0.649 0.650 0.616 0.650
 
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.046, 0.116, 1.01 0.028, 0.063, 1.02 0.023, 0.046, 1.07 0.025, 0.055, 1.06
No. of reflections 1024 2093 2691 2105
No. of parameters 58 115 173 116
H-atom treatment H-atom parameters constrained H-atom parameters constrained H-atom parameters constrained H-atom parameters constrained
Δρmax, Δρmin (e Å−3) 1.36, −1.28 0.44, −0.69 0.56, −0.49 0.44, −0.48
Computer programs: SMART, APEX2 and SAINT (Bruker, 2002[Bruker (2002). APEX2, SMART, SAINT, and SADABS. Bruker AXS, Inc., Madison, Wisconsin, USA.]), SHELXT (Sheldrick, 2015a[Sheldrick, G. M. (2015a). Acta Cryst. A71, 3-8.]), SHELXL2014 (Sheldrick, 2015b[Sheldrick, G. M. (2015b). Acta Cryst. C71, 3-8.]), Mercury (Macrae et al., 2008[Macrae, C. F., Bruno, I. J., Chisholm, J. A., Edgington, P. R., McCabe, P., Pidcock, E., Rodriguez-Monge, L., Taylor, R., van de Streek, J. & Wood, P. A. (2008). J. Appl. Cryst. 41, 466-470.]), SHELXTL (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]), enCIFer (Allen et al., 2004[Allen, F. H., Johnson, O., Shields, G. P., Smith, B. R. & Towler, M. (2004). J. Appl. Cryst. 37, 335-338.]), and publCIF (Westrip, 2010[Westrip, S. P. (2010). J. Appl. Cryst. 43, 920-925.]).

Supporting information


Chemical context top

The reported structures of 2,4,6-tri­bromo­benzo­nitrile (RCN, Figs. 1 and 2; Carter & Britton, 1972) and 1,3,5-tri­bromo-2-iso­cyano­benzene (RNC, Figs. 1 and 3; Carter et al., 1977) have two-dimensional layers of similarly arranged molecules, but the packing of adjacent layers is distinctly different. At the time, no explanation was offered. It was puzzling, given that the two compounds are isoelectronic, isosteric, and the principal inter­molecular inter­actions, CN···Br and NC···Br, are similar. Recent reports of polytype organic structures, such as picryl bromide (Parrish et al., 2008) and 5,6-di­methyl­benzofurazan 1-oxide (Britton et al., 2012) led to the idea that RCN and RNC might occur as polytypes. Earlier, Bredig (1930) had determined the space group and unit cell of RCN with the same results as Carter & Britton. Bredig was trying to follow up on the goniometer studies of Jaeger (1909), but while he found the same a:b ratio as Jaeger in the RCN unit cell, he found a different b:c ratio.

Accordingly, a search was made for polytypes of RCN, and to a lesser extent, of RNC. Four different structures were identified. RCN-I is the original Z = 2 structure of RCN; RCN-II is a new Z = 8 polytype; RCN-III is a new Z = 12 polytype. No RNC counterparts to RCN-I or RCN-III were observed. RNC-II is the original Z = 8 structure. As the Z values suggest, RCN-II and RNC-II are isomorphs.

Structural commentary top

Molecules of RCN and RNC are nearly planar. The average distance of atoms from the plane of best fit is 0.025 Å in RCN-I. For RCN-II, the average distances are 0.037 and 0.010 Å, for the (N27) and (N37) molecules, respectively. In RNC-II, the molecules are slightly more distorted, with average deviations of 0.043 and 0.017 Å for the (N127) and (N137) molecules, respectively. For RCN-III, the average distances are 0.009, 0.018, and 0.032 Å for the (N47), (N57), and (N67) molecules, respectively.

The bond lengths in RCN and RNC are generally similar (Fig. 4). They are also similar to the mean bond distances reported for bonds of each type (Allen et al., 1987). The N atom in RNC is displaced toward the aryl ring compared to the literature distances for aryl isocyanides.

Supra­molecular features top

Fig. 5 shows a two-dimensional layer of RCN-I. All of the structures are composed of similar layers. Adjacent molecules are associated through C N···Br inter­actions, arranged in R22(10) rings (Etter, 1990; Bernstein et al., 1995). The CN···Br distances in these rings range between 3.053 and 3.077 Å (Table 1); these distances can be compared with the N···Br van der Waals distance of 3.40 Å (Bondi, 1964; Rowland & Taylor, 1996). Each layer in RCN-II is composed of alternating (N27) and (N37) molecules. RCN-III contains two layers of alternating (N47) and (N57) molecules for each layer composed entirely of (N67) molecules. Adjacent pairs of layers show translational or pseudotranslational, or pseudocentric stacking (Fig. 6). RCN-I shows translational stacking between all adjacent layers (Fig 7). In RCN-II, alternating pairs of layers show pseudocentric and pseudotranslational stacking (Fig. 8). In RCN-III, each layer of (N67) molecules pseudotranslationally overlaps both neighboring (N47/N57) layers, while pairs of adjacent (N47/N57) layers, every third pair of layers, overlap pseudocentrically (Fig. 9).

The NC···Br contact distances in RNC-II are a smaller percentage of the van der Waals distance, 3.63 Å, versus corresponding atoms in RCN-II. The contacts in RNC-II occur at slightly wider angles than those in RCN-II (Table 1).

In RCN-II, the planes of best fit of the two different molecules are inclined by 6.5° to each other; in RNC-II this inclination is 7.5°. In RCN-III, the relative inclination of planes of (N47) and (N57) molecules is 7.0°. These two planes are approximately bis­ected by the planes of (N67) molecules.

Database survey top

A search of the Cambridge Structural Database (Version 5.36, update 3; Groom & Allen, 2014) for 2,4,6-trihalo-3,5-unsubstituted benzo­nitriles found nine entries: RCN; its tri­chloro analog, Gol'der et al. (1952), Carter & Britton (1972), Pink et al. (2000); its tri­fluoro analog, Britton (2008); four mixed-halogen entries, Gleason & Britton (1978), Britton (2005), Britton et al. (2002), and Britton (1997). Searching for the corresponding isocyanides found two entries: RNC and its tri­chloro analog (Pink et al., 2000).

Layers of the type observed in RCN were reported in 2,6-di­bromo entries with Cl, Br, or I at the 4-position. Other entries exhibit short contacts between the cyano- or iso­cyano- group and one ortho-halogen atom of an intra­layer molecule, with various inter­layer contacts. Polymorphs are only reported for 2,4,6-tri­chloro­benzo­nitrile; those are not polytypic.

Expanding the search to include organometallic complexes found three more entries, with the cyano N or iso­cyano C atom ligating gallium (tri­fluoro­benzo­nitrile; Tang et al., 2012), rhenium (tri­chloro­iso­cyano­benzene; Ko et al., 2011), and ruthenium (RNC; Leung et al., 2009).

Synthesis and crystallization top

2,4,6-Tri­bromo­aniline was prepared from aniline according to the work of Coleman & Talbot (1943).

RCN, adapted from the work of Toya et al. (1992): Diazo­tization: 2,4,6-Tri­bromo­aniline (1.25 g), water (2.5 ml), and glacial acetic acid (4.4 ml) were combined in a round-bottomed flask. The resulting suspension was cooled in an ice bath, and then H2SO4 (98%, 1.0 ml) was added dropwise, followed by an ice-cold solution of NaNO2 (520 mg) in water (4 ml). The resulting mixture was warmed to 310 K for 1 h, and then cooled in an ice bath. Cyanide suspension: CuCN (680 mg) and NaCN (1.12 g) were dissolved in water (20 ml). NaHCO3 (10.9 g) and ethyl acetate (10 ml) were added, giving a suspension, which was cooled in an ice bath. Cyanation: The diazo­tization mixture was added dropwise to the cyanide suspension as quickly as possible without causing excessive foaming. The ice bath was removed and then the mixture was stirred overnight. The organic phase was set aside. The aqueous phase was extracted with ethyl acetate (3 × 10 ml). The combined organic portions were washed with brine (10 ml), dried with Na2SO4, and concentrated at reduced pressure, giving a brown powder, which was purified by column chromatography (SiO2, hexane–ethyl acetate, gradient from 1:0 to 10:1). The desired fraction (Rf = 0.61 in 8:1) was concentrated at reduced pressure, giving beige needles (760 mg, 59 %). M.p. 400–400.5 K (lit. 402 K; Giumanini et al., 1996); 1H NMR (300 MHz, CD2Cl2) δ 7.853 (s, H13); 13C NMR (75 MHz, CD2Cl2) δ 135.3 (C13), 128.6 (C14), 127.4 (C12), 118.3 (C17), 116.0 (C11); IR (NaCl, cm–1) 3095, 3068, 2921 (w), 2233 (s, CN; lit. 2232), 1716 (w), 1563 (s), 1527 (s), 1431 (s), 1410 (s), 1370 (s), 1353 (s), 1328, 1191 (s), 1109 (s), 1087, 1063 (s), 854 (s), 809 (s), 748 (s); MS (EI, m/z) [M]+ calculated for C7H2Br3N 336.7732, found 336.7716.

2,4,6-Tri­bromo­formanilide, adapted from the work of Krishnamurthy (1982): Acetic anhydride (3.2 ml) and tetra­hydro­furan (THF, 5.0 ml) were combined in a round-bottomed flask. Formic acid (88 % aq., 1.7 ml) was added dropwise. The resulting solution was stirred for 30 min at room temperature. A solution of 2,4,6-tri­bromo­aniline (1.82 g) in THF (20 ml) was added dropwise. The resulting mixture was stirred for 18 h. The resulting heterogeneous mixture was filtered through neutral alumina (Sigma–Aldrich 199974, 5 cm H × 3 cm D), with addition of sufficient THF to elute all product, as indicated by TLC. The filtrate was concentrated at reduced pressure. The resulting residue was washed with sat. NaHCO3 solution (50 ml), and then filtered. The filter cake was recrystallized from acetone, giving white needles (1.72 g, 87 %). M.p. 493–494 K (lit. 494.5 K; Chattaway et al., 1899); Rf = 0.48 (SiO2 in 1:1 hexane–ethyl acetate); 1H NMR (300 MHz, (CD3)2SO) δ 10.192 (s, NH, O—E conformer, 0.87H), 8.522 (s, NH, O—Z conformer, 0.13H), 8.260 (s, CHO, 1H), 8.018 (s, CH, 2H); 13C NMR (75 MHz, (CD3)2SO) δ 165.9 (CO, O—Z conformer), 159.8 (CO, O—E conformer), 134.6 (ipso-C), 134.4 (CH), 124.5 (ortho-CBr), 121.1 (para-CBr); IR (NaCl, cm–1) 3201, 3166, 1661 (s, CO), 1558, 1154, 858, 810; MS (ESI, m/z) [M – H] calculated for C7H4Br3NO 355.7750, found 355.7758. Analysis (MHW Laboratories, Phoenix, AZ, USA) calculated for C7H4Br3NO: C 23.50, H 1.13, Br 66.99, N 3.91; found C 23.42, H 1.15, Br 66.71, N 3.57.

RNC, adapted from the work of Ugi et al. (1965): 2,4,6-Tri­bromo­formanilide (1.96 g) and N,N-diiso­propyl­ethyl­amine (DIPEA, 3.4 ml) were added to 1,2-di­chloro­ethane (75 ml). The resulting suspension was refluxed for 5 min, and then cooled to room temperature. POCl3 (0.6 ml) was added dropwise. The mixture was stirred for 18 h, cooled in an ice bath, and then filtered through neutral alumina (3 cm H × 3 cm D), with addition of sufficient di­chloro­methane (DCM) to elute all product as indicated by TLC. The filtrate was concentrated at reduced pressure. The resulting yellow residue was dissolved in DCM (25 ml), cooled in an ice bath, and washed with ice-cold acetic acid solution (0.025 M, 3 × 15 ml), and then ice-cold sat. NaHCO3 solution (15 ml). The organic phase was collected, dried with Na2SO4, and then concentrated under a stream of nitro­gen, giving beige needles upon filtration (630 mg, 34%). M.p. 390 K (lit. 394 K, Mironov & Mokrushin, 1999); Rf = 0.75 (Al2O3 in 2:1 hexane–ethyl acetate); 1H NMR (300 MHz, CD2Cl2) δ 7.827 (s, H123); 13C NMR (75 MHz, (CD3)2CO) 159.7 (C127), 135.8 (C123), 135.4 (C121), 124.5 (C124), 122.0 (C122); IR (NaCl, cm–1) 3162, 3068, 2921, 2128 (s, NC; lit. 2125), 1660 (s), 1555 (s), 1370 (s), 856 (s), 701 (s); MS (EI, m/z) [M]+ calculated for C7H2Br3N 336.7732, found 336.7734.

Crystallization: RCN crystals were grown by slow evaporation of single-solvent solutions (290–295 K). RCN-I was obtained from aceto­nitrile, benzene, chloro­form, or methyl­ene chloride; RCN-II from mesitylene; RCN-III from benzene or chloro­form. RNC-II crystals were obtained by sublimation (385 K, 0.05 torr), or by slow evaporation from the same solvents as RCN (268–295 K).

Refinement top

Crystal data, data collection, and structure refinement details for RCN and RNC are summarized in Table 2. H atoms were placed in calculated positions and refined as riding atoms, with C—H = 0.95 Å and Uiso(H) = 1.2Ueq(C).

Structure description top

The reported structures of 2,4,6-tri­bromo­benzo­nitrile (RCN, Figs. 1 and 2; Carter & Britton, 1972) and 1,3,5-tri­bromo-2-iso­cyano­benzene (RNC, Figs. 1 and 3; Carter et al., 1977) have two-dimensional layers of similarly arranged molecules, but the packing of adjacent layers is distinctly different. At the time, no explanation was offered. It was puzzling, given that the two compounds are isoelectronic, isosteric, and the principal inter­molecular inter­actions, CN···Br and NC···Br, are similar. Recent reports of polytype organic structures, such as picryl bromide (Parrish et al., 2008) and 5,6-di­methyl­benzofurazan 1-oxide (Britton et al., 2012) led to the idea that RCN and RNC might occur as polytypes. Earlier, Bredig (1930) had determined the space group and unit cell of RCN with the same results as Carter & Britton. Bredig was trying to follow up on the goniometer studies of Jaeger (1909), but while he found the same a:b ratio as Jaeger in the RCN unit cell, he found a different b:c ratio.

Accordingly, a search was made for polytypes of RCN, and to a lesser extent, of RNC. Four different structures were identified. RCN-I is the original Z = 2 structure of RCN; RCN-II is a new Z = 8 polytype; RCN-III is a new Z = 12 polytype. No RNC counterparts to RCN-I or RCN-III were observed. RNC-II is the original Z = 8 structure. As the Z values suggest, RCN-II and RNC-II are isomorphs.

Molecules of RCN and RNC are nearly planar. The average distance of atoms from the plane of best fit is 0.025 Å in RCN-I. For RCN-II, the average distances are 0.037 and 0.010 Å, for the (N27) and (N37) molecules, respectively. In RNC-II, the molecules are slightly more distorted, with average deviations of 0.043 and 0.017 Å for the (N127) and (N137) molecules, respectively. For RCN-III, the average distances are 0.009, 0.018, and 0.032 Å for the (N47), (N57), and (N67) molecules, respectively.

The bond lengths in RCN and RNC are generally similar (Fig. 4). They are also similar to the mean bond distances reported for bonds of each type (Allen et al., 1987). The N atom in RNC is displaced toward the aryl ring compared to the literature distances for aryl isocyanides.

Fig. 5 shows a two-dimensional layer of RCN-I. All of the structures are composed of similar layers. Adjacent molecules are associated through C N···Br inter­actions, arranged in R22(10) rings (Etter, 1990; Bernstein et al., 1995). The CN···Br distances in these rings range between 3.053 and 3.077 Å (Table 1); these distances can be compared with the N···Br van der Waals distance of 3.40 Å (Bondi, 1964; Rowland & Taylor, 1996). Each layer in RCN-II is composed of alternating (N27) and (N37) molecules. RCN-III contains two layers of alternating (N47) and (N57) molecules for each layer composed entirely of (N67) molecules. Adjacent pairs of layers show translational or pseudotranslational, or pseudocentric stacking (Fig. 6). RCN-I shows translational stacking between all adjacent layers (Fig 7). In RCN-II, alternating pairs of layers show pseudocentric and pseudotranslational stacking (Fig. 8). In RCN-III, each layer of (N67) molecules pseudotranslationally overlaps both neighboring (N47/N57) layers, while pairs of adjacent (N47/N57) layers, every third pair of layers, overlap pseudocentrically (Fig. 9).

The NC···Br contact distances in RNC-II are a smaller percentage of the van der Waals distance, 3.63 Å, versus corresponding atoms in RCN-II. The contacts in RNC-II occur at slightly wider angles than those in RCN-II (Table 1).

In RCN-II, the planes of best fit of the two different molecules are inclined by 6.5° to each other; in RNC-II this inclination is 7.5°. In RCN-III, the relative inclination of planes of (N47) and (N57) molecules is 7.0°. These two planes are approximately bis­ected by the planes of (N67) molecules.

A search of the Cambridge Structural Database (Version 5.36, update 3; Groom & Allen, 2014) for 2,4,6-trihalo-3,5-unsubstituted benzo­nitriles found nine entries: RCN; its tri­chloro analog, Gol'der et al. (1952), Carter & Britton (1972), Pink et al. (2000); its tri­fluoro analog, Britton (2008); four mixed-halogen entries, Gleason & Britton (1978), Britton (2005), Britton et al. (2002), and Britton (1997). Searching for the corresponding isocyanides found two entries: RNC and its tri­chloro analog (Pink et al., 2000).

Layers of the type observed in RCN were reported in 2,6-di­bromo entries with Cl, Br, or I at the 4-position. Other entries exhibit short contacts between the cyano- or iso­cyano- group and one ortho-halogen atom of an intra­layer molecule, with various inter­layer contacts. Polymorphs are only reported for 2,4,6-tri­chloro­benzo­nitrile; those are not polytypic.

Expanding the search to include organometallic complexes found three more entries, with the cyano N or iso­cyano C atom ligating gallium (tri­fluoro­benzo­nitrile; Tang et al., 2012), rhenium (tri­chloro­iso­cyano­benzene; Ko et al., 2011), and ruthenium (RNC; Leung et al., 2009).

Synthesis and crystallization top

2,4,6-Tri­bromo­aniline was prepared from aniline according to the work of Coleman & Talbot (1943).

RCN, adapted from the work of Toya et al. (1992): Diazo­tization: 2,4,6-Tri­bromo­aniline (1.25 g), water (2.5 ml), and glacial acetic acid (4.4 ml) were combined in a round-bottomed flask. The resulting suspension was cooled in an ice bath, and then H2SO4 (98%, 1.0 ml) was added dropwise, followed by an ice-cold solution of NaNO2 (520 mg) in water (4 ml). The resulting mixture was warmed to 310 K for 1 h, and then cooled in an ice bath. Cyanide suspension: CuCN (680 mg) and NaCN (1.12 g) were dissolved in water (20 ml). NaHCO3 (10.9 g) and ethyl acetate (10 ml) were added, giving a suspension, which was cooled in an ice bath. Cyanation: The diazo­tization mixture was added dropwise to the cyanide suspension as quickly as possible without causing excessive foaming. The ice bath was removed and then the mixture was stirred overnight. The organic phase was set aside. The aqueous phase was extracted with ethyl acetate (3 × 10 ml). The combined organic portions were washed with brine (10 ml), dried with Na2SO4, and concentrated at reduced pressure, giving a brown powder, which was purified by column chromatography (SiO2, hexane–ethyl acetate, gradient from 1:0 to 10:1). The desired fraction (Rf = 0.61 in 8:1) was concentrated at reduced pressure, giving beige needles (760 mg, 59 %). M.p. 400–400.5 K (lit. 402 K; Giumanini et al., 1996); 1H NMR (300 MHz, CD2Cl2) δ 7.853 (s, H13); 13C NMR (75 MHz, CD2Cl2) δ 135.3 (C13), 128.6 (C14), 127.4 (C12), 118.3 (C17), 116.0 (C11); IR (NaCl, cm–1) 3095, 3068, 2921 (w), 2233 (s, CN; lit. 2232), 1716 (w), 1563 (s), 1527 (s), 1431 (s), 1410 (s), 1370 (s), 1353 (s), 1328, 1191 (s), 1109 (s), 1087, 1063 (s), 854 (s), 809 (s), 748 (s); MS (EI, m/z) [M]+ calculated for C7H2Br3N 336.7732, found 336.7716.

2,4,6-Tri­bromo­formanilide, adapted from the work of Krishnamurthy (1982): Acetic anhydride (3.2 ml) and tetra­hydro­furan (THF, 5.0 ml) were combined in a round-bottomed flask. Formic acid (88 % aq., 1.7 ml) was added dropwise. The resulting solution was stirred for 30 min at room temperature. A solution of 2,4,6-tri­bromo­aniline (1.82 g) in THF (20 ml) was added dropwise. The resulting mixture was stirred for 18 h. The resulting heterogeneous mixture was filtered through neutral alumina (Sigma–Aldrich 199974, 5 cm H × 3 cm D), with addition of sufficient THF to elute all product, as indicated by TLC. The filtrate was concentrated at reduced pressure. The resulting residue was washed with sat. NaHCO3 solution (50 ml), and then filtered. The filter cake was recrystallized from acetone, giving white needles (1.72 g, 87 %). M.p. 493–494 K (lit. 494.5 K; Chattaway et al., 1899); Rf = 0.48 (SiO2 in 1:1 hexane–ethyl acetate); 1H NMR (300 MHz, (CD3)2SO) δ 10.192 (s, NH, O—E conformer, 0.87H), 8.522 (s, NH, O—Z conformer, 0.13H), 8.260 (s, CHO, 1H), 8.018 (s, CH, 2H); 13C NMR (75 MHz, (CD3)2SO) δ 165.9 (CO, O—Z conformer), 159.8 (CO, O—E conformer), 134.6 (ipso-C), 134.4 (CH), 124.5 (ortho-CBr), 121.1 (para-CBr); IR (NaCl, cm–1) 3201, 3166, 1661 (s, CO), 1558, 1154, 858, 810; MS (ESI, m/z) [M – H] calculated for C7H4Br3NO 355.7750, found 355.7758. Analysis (MHW Laboratories, Phoenix, AZ, USA) calculated for C7H4Br3NO: C 23.50, H 1.13, Br 66.99, N 3.91; found C 23.42, H 1.15, Br 66.71, N 3.57.

RNC, adapted from the work of Ugi et al. (1965): 2,4,6-Tri­bromo­formanilide (1.96 g) and N,N-diiso­propyl­ethyl­amine (DIPEA, 3.4 ml) were added to 1,2-di­chloro­ethane (75 ml). The resulting suspension was refluxed for 5 min, and then cooled to room temperature. POCl3 (0.6 ml) was added dropwise. The mixture was stirred for 18 h, cooled in an ice bath, and then filtered through neutral alumina (3 cm H × 3 cm D), with addition of sufficient di­chloro­methane (DCM) to elute all product as indicated by TLC. The filtrate was concentrated at reduced pressure. The resulting yellow residue was dissolved in DCM (25 ml), cooled in an ice bath, and washed with ice-cold acetic acid solution (0.025 M, 3 × 15 ml), and then ice-cold sat. NaHCO3 solution (15 ml). The organic phase was collected, dried with Na2SO4, and then concentrated under a stream of nitro­gen, giving beige needles upon filtration (630 mg, 34%). M.p. 390 K (lit. 394 K, Mironov & Mokrushin, 1999); Rf = 0.75 (Al2O3 in 2:1 hexane–ethyl acetate); 1H NMR (300 MHz, CD2Cl2) δ 7.827 (s, H123); 13C NMR (75 MHz, (CD3)2CO) 159.7 (C127), 135.8 (C123), 135.4 (C121), 124.5 (C124), 122.0 (C122); IR (NaCl, cm–1) 3162, 3068, 2921, 2128 (s, NC; lit. 2125), 1660 (s), 1555 (s), 1370 (s), 856 (s), 701 (s); MS (EI, m/z) [M]+ calculated for C7H2Br3N 336.7732, found 336.7734.

Crystallization: RCN crystals were grown by slow evaporation of single-solvent solutions (290–295 K). RCN-I was obtained from aceto­nitrile, benzene, chloro­form, or methyl­ene chloride; RCN-II from mesitylene; RCN-III from benzene or chloro­form. RNC-II crystals were obtained by sublimation (385 K, 0.05 torr), or by slow evaporation from the same solvents as RCN (268–295 K).

Refinement details top

Crystal data, data collection, and structure refinement details for RCN and RNC are summarized in Table 2. H atoms were placed in calculated positions and refined as riding atoms, with C—H = 0.95 Å and Uiso(H) = 1.2Ueq(C).

Computing details top

Data collection: SMART (Bruker, 2002) for RCN-I, RCN-II, RCN-III; APEX2 (Bruker, 2002) for RNC-II. For all compounds, cell refinement: SAINT (Bruker, 2002); data reduction: SAINT (Bruker, 2002). Program(s) used to solve structure: SHELXTL (Sheldrick, 2008) for RCN-I, RCN-II, RCN-III; SHELXT (Sheldrick, 2015a) for RNC-II. Program(s) used to refine structure: SHELXTL (Sheldrick, 2008) for RCN-I, RCN-II, RCN-III; SHELXL2014 (Sheldrick, 2015b) for RNC-II. For all compounds, molecular graphics: Mercury (Macrae et al., 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008), enCIFer (Allen et al., 2004), and publCIF (Westrip, 2010).

Figures top
[Figure 1] Fig. 1. Synthesis of RCN and RNC.
[Figure 2] Fig. 2. Molecular structures, with atom labeling, of RCN-I viewed along [111]; RCN-II viewed along [120]; RCN-III viewed along [120]. Displacement ellipsoids are drawn at the 50% probability level. In discussion, molecules are named by their respective nitrogen atoms. Each molecule lies across a crystallographic mirror plane.
[Figure 3] Fig. 3. Molecular structure, with atom labeling, of RNC-II viewed along [120]. Displacement ellipsoids are drawn at the 50% probability level. Each molecule lies across a crystallographic mirror plane.
[Figure 4] Fig. 4. Selected bond lengths (Å) in RCN and RNC, averaged across all polytypes. The data shown in parentheses are the mean distances for each bond type reported by Allen et al. (1987).
[Figure 5] Fig. 5. View of one layer of RCN-I along [101]. Dashed blue lines represent short contacts.
[Figure 6] Fig. 6. Pseudotranslational (T) and pseudocentric (C) stacking of layers in RCN-II and RCN-III, respectively. Both are viewed along [100]. The molecules shown are the second pair of layers from the top, in Fig. 7 and Fig. 8, respectively.
[Figure 7] Fig. 7. Translational (T) stacking of layers in Z = 2 RCN-I, viewed along [110]. If the unit cell of RCN-I is transformed by the matrix [100/010/201], the dimensions of the projection become 10.247 (3) × 12.480 (3) Å, which is similar to the corresponding b × c measurements, 10.2147 (10) × 12.4754 (12) Å for RCN-II, and 10.2167 (18) × 12.493 (2) Å for RCN-III.
[Figure 8] Fig. 8. Pseudocentric (C) and pseudotranslational (T) stacking of layers in Z = 8 RCN-II, viewed roughly along [010].
[Figure 9] Fig. 9. Pseudotranslational (T) and pseudocentric (C) stacking of layers in Z = 12 RCN-III, viewed roughly along [010].
(RCN-I) 2,4,6-Tribromobenzonitrile - polytype I top
Crystal data top
C7H2Br3NF(000) = 312
Mr = 339.83Dx = 2.612 Mg m3
Monoclinic, P21/mMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybCell parameters from 2049 reflections
a = 4.8742 (15) Åθ = 2.4–27.4°
b = 10.247 (3) ŵ = 13.93 mm1
c = 8.683 (3) ÅT = 173 K
β = 94.97 (1)°Needle, colorless
V = 432.0 (2) Å30.50 × 0.15 × 0.10 mm
Z = 2
Data collection top
Bruker 1K area-detector
diffractometer
1024 independent reflections
Radiation source: fine-focus sealed tube856 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.127
ω scansθmax = 27.5°, θmin = 2.4°
Absorption correction: multi-scan
(SADABS; Bruker, 2002)
h = 66
Tmin = 0.080, Tmax = 0.248k = 1313
4093 measured reflectionsl = 1111
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.046Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.116H-atom parameters constrained
S = 1.01 w = 1/[σ2(Fo2) + (0.069P)2]
where P = (Fo2 + 2Fc2)/3
1024 reflections(Δ/σ)max = 0.001
58 parametersΔρmax = 1.36 e Å3
0 restraintsΔρmin = 1.28 e Å3
Crystal data top
C7H2Br3NV = 432.0 (2) Å3
Mr = 339.83Z = 2
Monoclinic, P21/mMo Kα radiation
a = 4.8742 (15) ŵ = 13.93 mm1
b = 10.247 (3) ÅT = 173 K
c = 8.683 (3) Å0.50 × 0.15 × 0.10 mm
β = 94.97 (1)°
Data collection top
Bruker 1K area-detector
diffractometer
1024 independent reflections
Absorption correction: multi-scan
(SADABS; Bruker, 2002)
856 reflections with I > 2σ(I)
Tmin = 0.080, Tmax = 0.248Rint = 0.127
4093 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0460 restraints
wR(F2) = 0.116H-atom parameters constrained
S = 1.01Δρmax = 1.36 e Å3
1024 reflectionsΔρmin = 1.28 e Å3
58 parameters
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
Br120.33356 (11)0.47324 (5)0.18676 (7)0.0280 (2)
Br141.11323 (14)0.75000.57820 (9)0.0256 (3)
N170.0263 (14)0.75000.0147 (8)0.0313 (16)
C110.3828 (14)0.75000.1960 (8)0.0204 (15)
C120.4932 (10)0.6324 (5)0.2559 (6)0.0224 (11)
C130.7107 (10)0.6313 (5)0.3688 (6)0.0244 (11)
H130.78420.55120.40910.029*
C140.8200 (14)0.75000.4224 (8)0.0197 (15)
C170.1523 (16)0.75000.0799 (9)0.0241 (16)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Br120.0334 (4)0.0160 (3)0.0337 (4)0.0043 (2)0.0015 (2)0.0016 (2)
Br140.0229 (4)0.0239 (4)0.0295 (5)0.0000.0018 (3)0.000
N170.041 (4)0.021 (3)0.031 (4)0.0000.006 (3)0.000
C110.022 (3)0.025 (4)0.015 (4)0.0000.005 (3)0.000
C120.023 (2)0.016 (2)0.029 (3)0.0012 (19)0.006 (2)0.001 (2)
C130.024 (2)0.017 (3)0.033 (3)0.004 (2)0.007 (2)0.004 (2)
C140.024 (3)0.025 (4)0.011 (3)0.0000.003 (3)0.000
C170.030 (4)0.011 (3)0.032 (4)0.0000.004 (3)0.000
Geometric parameters (Å, º) top
Br12—C121.883 (5)C12—C131.380 (8)
Br14—C141.881 (7)C13—C141.391 (6)
C11—C121.401 (6)C13—H130.9500
C11—C171.443 (10)N17—C171.144 (10)
C12—C11—C12i118.6 (6)C12—C13—H13120.7
C12—C11—C17120.7 (3)C14—C13—H13120.7
C13—C12—C11121.2 (5)C13—C14—C13i121.9 (6)
C13—C12—Br12119.3 (4)C13—C14—Br14119.0 (3)
C11—C12—Br12119.4 (4)N17—C17—C11178.4 (9)
C12—C13—C14118.6 (5)
C12i—C11—C12—C131.6 (11)C11—C12—C13—C140.2 (10)
C17—C11—C12—C13178.9 (7)Br12—C12—C13—C14177.8 (5)
C12i—C11—C12—Br12176.0 (3)C12—C13—C14—C13i2.0 (12)
C17—C11—C12—Br121.3 (9)C12—C13—C14—Br14179.2 (5)
Symmetry code: (i) x, y+3/2, z.
(RCN-II) 2,4,6-Tribromobenzonitrile - polytype II top
Crystal data top
C7H2Br3NF(000) = 1248
Mr = 339.83Dx = 2.601 Mg m3
Orthorhombic, PnmaMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ac 2nCell parameters from 3180 reflections
a = 13.6183 (13) Åθ = 2.9–27.2°
b = 10.2147 (10) ŵ = 13.88 mm1
c = 12.4754 (12) ÅT = 173 K
V = 1735.4 (3) Å3Plate, colorless
Z = 80.25 × 0.20 × 0.07 mm
Data collection top
Bruker 1K area-detector
diffractometer
2093 independent reflections
Radiation source: fine-focus sealed tube1692 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.052
ω scansθmax = 27.5°, θmin = 2.2°
Absorption correction: multi-scan
(SADABS; Bruker, 2002)
h = 1717
Tmin = 0.06, Tmax = 0.37k = 1313
16607 measured reflectionsl = 1616
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.028Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.063H-atom parameters constrained
S = 1.02 w = 1/[σ2(Fo2) + (0.030P)2 + 1.560P]
where P = (Fo2 + 2Fc2)/3
2093 reflections(Δ/σ)max = 0.001
115 parametersΔρmax = 0.44 e Å3
0 restraintsΔρmin = 0.69 e Å3
Crystal data top
C7H2Br3NV = 1735.4 (3) Å3
Mr = 339.83Z = 8
Orthorhombic, PnmaMo Kα radiation
a = 13.6183 (13) ŵ = 13.88 mm1
b = 10.2147 (10) ÅT = 173 K
c = 12.4754 (12) Å0.25 × 0.20 × 0.07 mm
Data collection top
Bruker 1K area-detector
diffractometer
2093 independent reflections
Absorption correction: multi-scan
(SADABS; Bruker, 2002)
1692 reflections with I > 2σ(I)
Tmin = 0.06, Tmax = 0.37Rint = 0.052
16607 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0280 restraints
wR(F2) = 0.063H-atom parameters constrained
S = 1.02Δρmax = 0.44 e Å3
2093 reflectionsΔρmin = 0.69 e Å3
115 parameters
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
Br220.13341 (3)0.52761 (3)0.04244 (3)0.02658 (11)
Br240.14558 (4)0.25000.43375 (4)0.02477 (13)
C210.1318 (3)0.25000.0608 (4)0.0197 (10)
C220.1359 (2)0.3683 (3)0.1174 (3)0.0206 (7)
C230.1418 (2)0.3697 (3)0.2282 (3)0.0217 (7)
H230.14440.45000.26660.026*
C240.1437 (3)0.25000.2821 (4)0.0190 (10)
C270.1207 (4)0.25000.0545 (4)0.0257 (11)
N270.1115 (3)0.25000.1447 (4)0.0332 (11)
Br320.10699 (3)0.47273 (3)0.69146 (3)0.02650 (11)
Br340.12804 (4)0.75000.29979 (4)0.02786 (13)
C310.1095 (3)0.75000.6720 (3)0.0175 (9)
C320.1116 (2)0.6320 (3)0.6155 (3)0.0195 (7)
C330.1171 (2)0.6315 (3)0.5049 (3)0.0201 (7)
H330.11890.55110.46660.024*
C340.1199 (3)0.75000.4508 (4)0.0196 (10)
C370.1056 (3)0.75000.7873 (4)0.0200 (10)
N370.1015 (3)0.75000.8798 (3)0.0255 (9)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Br220.0364 (2)0.01742 (19)0.0259 (2)0.00058 (15)0.00196 (15)0.00451 (14)
Br240.0303 (3)0.0261 (3)0.0179 (2)0.0000.00098 (19)0.000
C210.018 (2)0.021 (3)0.021 (2)0.0000.0017 (19)0.000
C220.0208 (16)0.0182 (16)0.0227 (17)0.0016 (14)0.0003 (13)0.0017 (14)
C230.0225 (16)0.0186 (18)0.0240 (17)0.0012 (14)0.0012 (14)0.0017 (14)
C240.021 (2)0.021 (3)0.015 (2)0.0000.0022 (18)0.000
C270.028 (3)0.020 (3)0.029 (3)0.0000.000 (2)0.000
N270.048 (3)0.026 (2)0.026 (3)0.0000.002 (2)0.000
Br320.0386 (2)0.01618 (19)0.02475 (19)0.00117 (15)0.00205 (14)0.00374 (14)
Br340.0418 (3)0.0243 (3)0.0174 (2)0.0000.0003 (2)0.000
C310.017 (2)0.021 (2)0.015 (2)0.0000.0003 (17)0.000
C320.0182 (15)0.0163 (16)0.0241 (17)0.0004 (13)0.0006 (13)0.0044 (14)
C330.0229 (17)0.0157 (18)0.0216 (17)0.0015 (14)0.0009 (13)0.0018 (14)
C340.025 (2)0.018 (2)0.015 (2)0.0000.0001 (18)0.000
C370.023 (2)0.014 (2)0.023 (3)0.0000.0009 (19)0.000
N370.030 (2)0.024 (2)0.023 (2)0.0000.0002 (17)0.000
Geometric parameters (Å, º) top
Br22—C221.877 (3)Br32—C321.884 (3)
Br24—C241.892 (5)Br34—C341.887 (4)
C21—C221.400 (4)C31—C321.396 (4)
C21—C271.446 (7)C31—C371.439 (6)
C22—C231.385 (5)C32—C331.382 (5)
C23—C241.395 (4)C33—C341.387 (4)
C23—H230.9500C33—H330.9500
C27—N271.132 (7)C37—N371.156 (6)
C22i—C21—C22119.3 (4)C32ii—C31—C32119.3 (4)
C22—C21—C27120.3 (2)C32—C31—C37120.3 (2)
C23—C22—C21120.9 (3)C33—C32—C31120.6 (3)
C23—C22—Br22119.3 (3)C33—C32—Br32120.0 (3)
C21—C22—Br22119.8 (3)C31—C32—Br32119.4 (2)
C22—C23—C24118.2 (3)C32—C33—C34118.9 (3)
C22—C23—H23120.9C32—C33—H33120.5
C24—C23—H23120.9C34—C33—H33120.5
C23i—C24—C23122.4 (4)C33ii—C34—C33121.6 (4)
C23—C24—Br24118.8 (2)C33—C34—Br34119.2 (2)
N27—C27—C21179.7 (5)N37—C37—C31179.3 (5)
C22i—C21—C22—C231.4 (6)C32ii—C31—C32—C330.8 (6)
C27—C21—C22—C23176.8 (4)C37—C31—C32—C33178.9 (4)
C22i—C21—C22—Br22178.6 (2)C32ii—C31—C32—Br32179.2 (2)
C27—C21—C22—Br223.2 (5)C37—C31—C32—Br321.1 (5)
C21—C22—C23—C240.1 (5)C31—C32—C33—C340.3 (5)
Br22—C22—C23—C24179.9 (3)Br32—C32—C33—C34179.7 (3)
C22—C23—C24—C23i1.3 (7)C32—C33—C34—C33ii0.2 (7)
C22—C23—C24—Br24177.1 (2)C32—C33—C34—Br34179.7 (2)
Symmetry codes: (i) x, y+1/2, z; (ii) x, y+3/2, z.
(RCN-III) 2,4,6-Tribromobenzonitrile - polytype III top
Crystal data top
C7H2Br3NF(000) = 1872
Mr = 339.83Dx = 2.601 Mg m3
Orthorhombic, PnmaMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ac 2nCell parameters from 2928 reflections
a = 20.399 (4) Åθ = 2.6–26.7°
b = 10.2167 (18) ŵ = 13.87 mm1
c = 12.493 (2) ÅT = 173 K
V = 2603.7 (8) Å3Needle, colorless
Z = 120.50 × 0.15 × 0.10 mm
Data collection top
Bruker 1K area-detector
diffractometer
2691 independent reflections
Radiation source: fine-focus sealed tube2165 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.055
ω scansθmax = 26.0°, θmin = 2.6°
Absorption correction: multi-scan
(SADABS; Bruker, 2002)
h = 2424
Tmin = 0.054, Tmax = 0.337k = 1212
22804 measured reflectionsl = 1515
Refinement top
Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: fullHydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.023H-atom parameters constrained
wR(F2) = 0.046 w = 1/[σ2(Fo2) + (0.0096P)2 + 3.390P]
where P = (Fo2 + 2Fc2)/3
S = 1.07(Δ/σ)max = 0.001
2691 reflectionsΔρmax = 0.56 e Å3
173 parametersΔρmin = 0.49 e Å3
0 restraintsExtinction correction: SHELXL, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
Primary atom site location: structure-invariant direct methodsExtinction coefficient: 0.00028 (3)
Crystal data top
C7H2Br3NV = 2603.7 (8) Å3
Mr = 339.83Z = 12
Orthorhombic, PnmaMo Kα radiation
a = 20.399 (4) ŵ = 13.87 mm1
b = 10.2167 (18) ÅT = 173 K
c = 12.493 (2) Å0.50 × 0.15 × 0.10 mm
Data collection top
Bruker 1K area-detector
diffractometer
2691 independent reflections
Absorption correction: multi-scan
(SADABS; Bruker, 2002)
2165 reflections with I > 2σ(I)
Tmin = 0.054, Tmax = 0.337Rint = 0.055
22804 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0230 restraints
wR(F2) = 0.046H-atom parameters constrained
S = 1.07Δρmax = 0.56 e Å3
2691 reflectionsΔρmin = 0.49 e Å3
173 parameters
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
Br420.340999 (16)0.52705 (3)0.05464 (3)0.02707 (10)
Br440.32895 (2)0.25000.33679 (4)0.02913 (13)
Br520.332551 (16)0.47245 (3)0.59427 (3)0.02775 (9)
Br540.32011 (2)0.75000.20370 (3)0.02542 (12)
Br620.511839 (16)0.52774 (3)0.67598 (3)0.02743 (10)
Br640.50730 (2)0.25001.06666 (4)0.02435 (12)
C410.33919 (19)0.25000.0353 (3)0.0182 (9)
C420.33772 (14)0.3675 (3)0.0214 (2)0.0207 (7)
C430.33432 (14)0.3686 (3)0.1321 (2)0.0226 (7)
H430.33310.44870.17060.027*
C440.3328 (2)0.25000.1851 (4)0.0219 (10)
C470.3440 (2)0.25000.1508 (4)0.0218 (10)
N470.34814 (18)0.25000.2423 (3)0.0272 (9)
C510.3338 (2)0.75000.5758 (4)0.0221 (10)
C520.33096 (14)0.6320 (3)0.5193 (2)0.0211 (7)
C530.32641 (14)0.6314 (3)0.4085 (2)0.0228 (7)
H530.32460.55120.37010.027*
C540.3245 (2)0.75000.3549 (3)0.0204 (10)
C570.3399 (2)0.75000.6908 (4)0.0225 (10)
N570.3445 (2)0.75000.7823 (3)0.0329 (10)
C610.5080 (2)0.25000.6942 (4)0.0204 (10)
C620.50889 (14)0.3676 (3)0.7509 (2)0.0216 (7)
C630.50886 (14)0.3686 (3)0.8618 (2)0.0218 (7)
H630.50920.44880.90020.026*
C640.5083 (2)0.25000.9155 (4)0.0200 (10)
C670.5049 (2)0.25000.5783 (4)0.0225 (10)
N670.5024 (2)0.25000.4872 (3)0.0329 (10)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Br420.03864 (19)0.01711 (17)0.02545 (18)0.00178 (14)0.00143 (15)0.00391 (15)
Br440.0432 (3)0.0252 (3)0.0190 (3)0.0000.0007 (2)0.000
Br520.03826 (19)0.01818 (17)0.02682 (18)0.00040 (15)0.00267 (15)0.00467 (15)
Br540.0309 (3)0.0270 (3)0.0184 (2)0.0000.0017 (2)0.000
Br620.03877 (19)0.01736 (17)0.02617 (18)0.00080 (15)0.00036 (15)0.00376 (15)
Br640.0300 (2)0.0243 (3)0.0188 (2)0.0000.00018 (19)0.000
C410.016 (2)0.017 (2)0.022 (2)0.0000.0010 (18)0.000
C420.0214 (15)0.0175 (17)0.0233 (17)0.0001 (14)0.0011 (13)0.0052 (14)
C430.0269 (16)0.0160 (17)0.0248 (17)0.0016 (14)0.0003 (14)0.0016 (15)
C440.023 (2)0.024 (3)0.019 (2)0.0000.0000 (19)0.000
C470.020 (2)0.016 (2)0.029 (3)0.0000.004 (2)0.000
N470.033 (2)0.022 (2)0.026 (2)0.0000.0017 (19)0.000
C510.016 (2)0.026 (3)0.024 (2)0.0000.001 (2)0.000
C520.0244 (15)0.0154 (17)0.0234 (16)0.0002 (14)0.0002 (13)0.0037 (14)
C530.0255 (16)0.0198 (18)0.0232 (17)0.0025 (14)0.0024 (14)0.0031 (15)
C540.020 (2)0.024 (3)0.017 (2)0.0000.0021 (18)0.000
C570.025 (2)0.015 (2)0.027 (3)0.0000.003 (2)0.000
N570.048 (3)0.027 (2)0.024 (2)0.0000.001 (2)0.000
C610.020 (2)0.022 (2)0.020 (2)0.0000.0041 (19)0.000
C620.0199 (15)0.0188 (17)0.0261 (17)0.0017 (13)0.0011 (13)0.0047 (15)
C630.0236 (16)0.0178 (18)0.0239 (16)0.0007 (14)0.0018 (13)0.0028 (15)
C640.020 (2)0.022 (2)0.018 (2)0.0000.0017 (19)0.000
C670.028 (2)0.016 (2)0.024 (3)0.0000.000 (2)0.000
N670.055 (3)0.021 (2)0.024 (2)0.0000.002 (2)0.000
Geometric parameters (Å, º) top
Br42—C421.888 (3)C51—C521.399 (4)
Br44—C441.897 (5)C51—C571.443 (6)
Br52—C521.880 (3)C52—C531.387 (4)
Br54—C541.892 (4)C53—C541.384 (4)
Br62—C621.885 (3)C53—H530.9500
Br64—C641.889 (4)C57—N571.147 (6)
C41—C421.394 (4)C61—C621.395 (4)
C41—C471.447 (6)C61—C671.450 (6)
C42—C431.384 (4)C62—C631.386 (4)
C43—C441.381 (4)C63—C641.385 (4)
C43—H430.9500C63—H630.9500
C47—N471.146 (6)C67—N671.139 (6)
C42—C41—C42i118.9 (4)C54—C53—H53120.6
C42—C41—C47120.5 (2)C52—C53—H53120.6
C43—C42—C41121.0 (3)C53ii—C54—C53122.1 (4)
C43—C42—Br42119.9 (2)C53—C54—Br54119.0 (2)
C41—C42—Br42119.2 (2)N57—C57—C51179.8 (5)
C44—C43—C42118.3 (3)C62i—C61—C62119.0 (4)
C44—C43—H43120.9C62—C61—C67120.5 (2)
C42—C43—H43120.9C63—C62—C61120.9 (3)
C43i—C44—C43122.6 (4)C63—C62—Br62119.4 (3)
C43—C44—Br44118.7 (2)C61—C62—Br62119.8 (2)
N47—C47—C41179.7 (5)C64—C63—C62118.6 (3)
C52ii—C51—C52119.1 (4)C64—C63—H63120.7
C52—C51—C57120.4 (2)C62—C63—H63120.7
C53—C52—C51120.7 (3)C63i—C64—C63122.0 (4)
C53—C52—Br52119.7 (2)C63—C64—Br64119.0 (2)
C51—C52—Br52119.7 (2)N67—C67—C61180.0 (5)
C54—C53—C52118.7 (3)
C42i—C41—C42—C430.5 (6)C51—C52—C53—C540.2 (5)
C47—C41—C42—C43178.8 (3)Br52—C52—C53—C54179.2 (3)
C42i—C41—C42—Br42179.07 (19)C52—C53—C54—C53ii0.6 (6)
C47—C41—C42—Br420.8 (5)C52—C53—C54—Br54178.7 (2)
C41—C42—C43—C440.4 (5)C62i—C61—C62—C631.7 (6)
Br42—C42—C43—C44179.2 (3)C67—C61—C62—C63177.0 (3)
C42—C43—C44—C43i0.2 (6)C62i—C61—C62—Br62177.1 (2)
C42—C43—C44—Br44179.4 (2)C67—C61—C62—Br624.2 (5)
C52ii—C51—C52—C530.9 (6)C61—C62—C63—C640.4 (5)
C57—C51—C52—C53178.7 (3)Br62—C62—C63—C64178.4 (3)
C52ii—C51—C52—Br52178.48 (19)C62—C63—C64—C63i1.0 (6)
C57—C51—C52—Br521.9 (5)C62—C63—C64—Br64179.3 (2)
Symmetry codes: (i) x, y+1/2, z; (ii) x, y+3/2, z.
(RNC-II) 1,3,5-Tribromo-2-isocyanobenzene - polytype II top
Crystal data top
C7H2Br3NDx = 2.595 Mg m3
Mr = 339.83Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, PnmaCell parameters from 2721 reflections
a = 13.5916 (18) Åθ = 3.0–27.4°
b = 10.1464 (13) ŵ = 13.84 mm1
c = 12.6158 (16) ÅT = 173 K
V = 1739.8 (4) Å3Block, colourless
Z = 80.40 × 0.35 × 0.20 mm
F(000) = 1248
Data collection top
Bruker APEXII CCD
diffractometer
1638 reflections with I > 2σ(I)
Radiation source: sealed tubeRint = 0.078
φ and ω scansθmax = 27.5°, θmin = 2.2°
Absorption correction: multi-scan
(SADABS; Bruker, 2002)
h = 1717
Tmin = 0.170, Tmax = 0.333k = 1313
19459 measured reflectionsl = 1616
2105 independent reflections
Refinement top
Refinement on F2Hydrogen site location: inferred from neighbouring sites
Least-squares matrix: fullH-atom parameters constrained
R[F2 > 2σ(F2)] = 0.025 w = 1/[σ2(Fo2) + (0.0121P)2 + 1.0004P]
where P = (Fo2 + 2Fc2)/3
wR(F2) = 0.055(Δ/σ)max = 0.001
S = 1.06Δρmax = 0.44 e Å3
2105 reflectionsΔρmin = 0.48 e Å3
116 parametersExtinction correction: SHELXL, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
0 restraintsExtinction coefficient: 0.00269 (12)
Crystal data top
C7H2Br3NV = 1739.8 (4) Å3
Mr = 339.83Z = 8
Orthorhombic, PnmaMo Kα radiation
a = 13.5916 (18) ŵ = 13.84 mm1
b = 10.1464 (13) ÅT = 173 K
c = 12.6158 (16) Å0.40 × 0.35 × 0.20 mm
Data collection top
Bruker APEXII CCD
diffractometer
2105 independent reflections
Absorption correction: multi-scan
(SADABS; Bruker, 2002)
1638 reflections with I > 2σ(I)
Tmin = 0.170, Tmax = 0.333Rint = 0.078
19459 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0250 restraints
wR(F2) = 0.055H-atom parameters constrained
S = 1.06Δρmax = 0.44 e Å3
2105 reflectionsΔρmin = 0.48 e Å3
116 parameters
Special details top

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
C1210.3678 (3)0.75000.5680 (3)0.0162 (9)
C1220.3637 (2)0.6315 (3)0.6238 (2)0.0176 (7)
C1230.3573 (2)0.6306 (3)0.7332 (2)0.0182 (7)
H1230.35410.54990.77120.022*
C1240.3559 (3)0.75000.7858 (4)0.0173 (9)
N1270.3793 (3)0.75000.4583 (3)0.0215 (9)
C1270.3909 (4)0.75000.3682 (4)0.0285 (12)
Br1220.36763 (3)0.47074 (3)0.54952 (3)0.02456 (11)
Br1240.35282 (4)0.75000.93610 (4)0.02254 (13)
C1310.3904 (3)0.25000.1747 (3)0.0161 (10)
C1320.3885 (2)0.3685 (3)0.1192 (3)0.0169 (7)
C1330.3821 (2)0.3691 (3)0.0100 (2)0.0179 (7)
H1330.38060.44990.02810.021*
C1340.3781 (3)0.25000.0428 (4)0.0190 (10)
N1370.3955 (3)0.25000.2840 (3)0.0180 (8)
C1370.3995 (3)0.25000.3761 (4)0.0246 (11)
Br1320.39399 (3)0.52885 (3)0.19404 (3)0.02480 (11)
Br1340.36801 (4)0.25000.19267 (4)0.02564 (14)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
C1210.013 (2)0.019 (2)0.016 (2)0.0000.0002 (19)0.000
C1220.0164 (16)0.0157 (16)0.0207 (17)0.0016 (14)0.0016 (14)0.0031 (13)
C1230.0191 (17)0.0152 (17)0.0202 (17)0.0013 (14)0.0017 (14)0.0039 (13)
C1240.017 (2)0.017 (2)0.018 (2)0.0000.0003 (19)0.000
N1270.026 (2)0.018 (2)0.021 (2)0.0000.0008 (17)0.000
C1270.035 (3)0.025 (3)0.026 (3)0.0000.002 (2)0.000
Br1220.0339 (2)0.01579 (18)0.0239 (2)0.00052 (15)0.00210 (15)0.00522 (14)
Br1240.0290 (3)0.0231 (3)0.0155 (2)0.0000.0005 (2)0.000
C1310.014 (2)0.019 (2)0.015 (2)0.0000.0026 (17)0.000
C1320.0158 (16)0.0138 (16)0.0210 (17)0.0001 (13)0.0003 (13)0.0042 (13)
C1330.0229 (18)0.0132 (17)0.0174 (17)0.0014 (14)0.0001 (13)0.0035 (13)
C1340.018 (2)0.024 (3)0.015 (2)0.0000.0016 (18)0.000
N1370.019 (2)0.017 (2)0.018 (2)0.0000.0008 (16)0.000
C1370.024 (3)0.019 (3)0.030 (3)0.0000.001 (2)0.000
Br1320.0360 (2)0.01500 (19)0.0234 (2)0.00111 (15)0.00260 (14)0.00427 (14)
Br1340.0393 (3)0.0222 (3)0.0154 (3)0.0000.0003 (2)0.000
Geometric parameters (Å, º) top
C121—N1271.393 (6)C131—N1371.380 (6)
C121—C122i1.395 (4)C131—C132ii1.392 (4)
C122—C1231.382 (4)C132—C1331.380 (4)
C122—Br1221.882 (3)C132—Br1321.883 (3)
C123—C124i1.381 (4)C133—C134ii1.381 (4)
C123—H1230.9500C133—H1330.9500
C124—Br1241.897 (5)C134—Br1341.895 (4)
N127—C1271.147 (6)N137—C1371.164 (6)
N127—C121—C122i120.4 (2)N137—C131—C132ii120.3 (2)
C122—C121—C122i119.1 (4)C132ii—C131—C132119.5 (4)
C123—C122—C121120.8 (3)C133—C132—C131120.5 (3)
C123—C122—Br122119.6 (2)C133—C132—Br132119.9 (2)
C121—C122—Br122119.6 (2)C131—C132—Br132119.5 (2)
C124—C123—C122118.3 (3)C132—C133—C134118.7 (3)
C124—C123—H123120.8C132—C133—H133120.7
C122—C123—H123120.8C134—C133—H133120.7
C123—C124—C123i122.5 (4)C133ii—C134—C133122.1 (4)
C123i—C124—Br124118.7 (2)C133ii—C134—Br134118.9 (2)
C127—N127—C121178.5 (5)C137—N137—C131179.8 (4)
N127—C121—C122—C123176.7 (3)N137—C131—C132—C133179.2 (3)
C122i—C121—C122—C1231.0 (6)C132ii—C131—C132—C1331.6 (6)
N127—C121—C122—Br1223.0 (5)N137—C131—C132—Br1320.6 (5)
C122i—C121—C122—Br122179.30 (19)C132ii—C131—C132—Br132178.6 (2)
C121—C122—C123—C1240.5 (5)C131—C132—C133—C1340.2 (5)
Br122—C122—C123—C124179.2 (3)Br132—C132—C133—C134179.9 (3)
C122—C123—C124—C123i2.1 (7)C132—C133—C134—C133ii1.3 (7)
C122—C123—C124—Br124177.4 (2)C132—C133—C134—Br134179.3 (3)
Symmetry codes: (i) x, y+3/2, z; (ii) x, y+1/2, z.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
C123—H123···Br134iii0.953.083.976 (3)157
C133—H133···Br124iv0.953.103.995 (3)157
Symmetry codes: (iii) x, y, z+1; (iv) x, y, z1.
Short contact geometry (Å, °) top
XY···BrXYY···BrXY···Br
C17N17···Br12i1.144 (10)3.053 (4)131.45 (9)
C27N27···Br32ii1.132 (7)3.059 (3)131.76 (7)
N127C127···Br132ii1.147 (6)3.141 (4)134.01 (8)
C37N37···Br22iii1.156 (6)3.077 (3)130.68 (10)
N137C137···Br122iii1.164 (6)3.161 (4)133.23 (11)
C47N47···Br52ii1.146 (6)3.072 (3)130.95 (9)
C57N57···Br42iii1.147 (6)3.057 (3)131.47 (7)
C67N67···Br62iv1.139 (6)3.065 (3)131.96 (7)
Symmetry codes: (i) -x, 1 - y, -z; (ii) x, y, -1 + z; (iii) x, y, 1 + z; (iv) 1 - x, 1 - y, 1 - z.

Experimental details

(RCN-I)(RCN-II)(RCN-III)(RNC-II)
Crystal data
Chemical formulaC7H2Br3NC7H2Br3NC7H2Br3NC7H2Br3N
Mr339.83339.83339.83339.83
Crystal system, space groupMonoclinic, P21/mOrthorhombic, PnmaOrthorhombic, PnmaOrthorhombic, Pnma
Temperature (K)173173173173
a, b, c (Å)4.8742 (15), 10.247 (3), 8.683 (3)13.6183 (13), 10.2147 (10), 12.4754 (12)20.399 (4), 10.2167 (18), 12.493 (2)13.5916 (18), 10.1464 (13), 12.6158 (16)
α, β, γ (°)90, 94.97 (1), 9090, 90, 9090, 90, 9090, 90, 90
V3)432.0 (2)1735.4 (3)2603.7 (8)1739.8 (4)
Z28128
Radiation typeMo KαMo KαMo KαMo Kα
µ (mm1)13.9313.8813.8713.84
Crystal size (mm)0.50 × 0.15 × 0.100.25 × 0.20 × 0.070.50 × 0.15 × 0.100.40 × 0.35 × 0.20
Data collection
DiffractometerBruker 1K area-detector
diffractometer
Bruker 1K area-detector
diffractometer
Bruker 1K area-detector
diffractometer
Bruker APEXII CCD
Absorption correctionMulti-scan
(SADABS; Bruker, 2002)
Multi-scan
(SADABS; Bruker, 2002)
Multi-scan
(SADABS; Bruker, 2002)
Multi-scan
(SADABS; Bruker, 2002)
Tmin, Tmax0.080, 0.2480.06, 0.370.054, 0.3370.170, 0.333
No. of measured, independent and
observed [I > 2σ(I)] reflections
4093, 1024, 856 16607, 2093, 1692 22804, 2691, 2165 19459, 2105, 1638
Rint0.1270.0520.0550.078
(sin θ/λ)max1)0.6490.6500.6160.650
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.046, 0.116, 1.01 0.028, 0.063, 1.02 0.023, 0.046, 1.07 0.025, 0.055, 1.06
No. of reflections1024209326912105
No. of parameters58115173116
H-atom treatmentH-atom parameters constrainedH-atom parameters constrainedH-atom parameters constrainedH-atom parameters constrained
Δρmax, Δρmin (e Å3)1.36, 1.280.44, 0.690.56, 0.490.44, 0.48

Computer programs: SMART (Bruker, 2002), APEX2 (Bruker, 2002), SAINT (Bruker, 2002), SHELXT (Sheldrick, 2015a), SHELXL2014 (Sheldrick, 2015b), Mercury (Macrae et al., 2008), SHELXTL (Sheldrick, 2008), enCIFer (Allen et al., 2004), and publCIF (Westrip, 2010).

 

Footnotes

Deceased July 7, 2015.

Acknowledgements

The authors thank Victor G. Young, Jr. (X-Ray Crystallographic Laboratory, University of Minnesota) for assistance with unit cell and crystal determinations, and the Wayland E. Noland Research Fellowship Fund at the University of Minnesota Foundation for generous financial support of this project.

References

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Volume 72| Part 2| February 2016| Pages 178-183
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